Subdiaphragmatic vagotomy abolishes increase in ornithine decarboxylase activity of rat duodenal mucosa after ischemia-reperfusion in superior mesenteric artery

Newly synthesized histamine accelerates ornithine decarboxylase activity in rat intestinal mucosa after ischemia-reperfusion

We previously demonstrated that both histamine synthesis (histidine decarboxylase activity) and polyamine synthesis (ornithine decarboxylase activity) increased in the rat intestinal mucosa after ischemia-reperfusion, whereas the relationship between these two factors remains unclear. To elucidate this relationship, we performed the present study. The superior mesenteric artery was occluded for 15 min followed by reperfusion. After ischemia-reperfusion, histidine decarboxylase activity and ornithine decarboxylase activity in the rat jejunal mucosa were measured in a time-dependent manner. Histidine decarboxylase activity increased 1 hr after ischemia-reperfusion, although ornithine decarboxylase activity did not; however, its activity did increase 6 hr after. The increase of ornithine decarboxylase activity was attenuated when the increase of histamine synthesis was suppressed by the inhibition of histidine decarboxylase activity caused by pretreatment with alpha-fluoromethylhistidine, a suicide inhibitor of histidine decarboxylase. Pretreatment with H1-receptor antagonist attenuated the increase of ornithine decarboxylase activity after ischemia-reperfusion. These results indicate that the newly synthesized histamine, as indicated by an increase of histidine decarboxylase activity, increases ornithine decarboxylase activity after ischemia-reperfusion of the rat intestinal mucosa.

Role of histamine receptors in intestinal repair after ischemia-reperfusion in rats

BACKGROUND/AIMS

Previously, we showed that an elevated production of histamine promotes the healing of injured intestinal mucosa after ischemia-reperfusion. The aim of the present study was to determine whether histamine-mediated repair of the intestinal mucosa after ischemia-reperfusion involves the engagement of H1 or H2 receptors.

METHODS

The superior mesenteric artery was occluded for 15 minutes followed by reperfusion, and H1- or H2-receptor antagonists were infused intraduodenally. After ischemia-reperfusion, ornithine decarboxylase activity in the jejunal mucosa and lipid transport to mesenteric lymph were examined.

RESULTS

In jejunal mucosa, ornithine decarboxylase activity markedly increased at 6 hours after reperfusion and remained elevated at 48 hours. The ischemia-reperfusion-induced increase in ornithine decarboxylase activity was attenuated (in a dose-dependent manner) by an H1-receptor antagonist (chlorpheniramine maleate) but not by an H2 antagonist (cimetidine). Intraperitoneal injection of an H3 antagonist (thioperamide) increased histamine output in mesenteric lymph and stimulated intestinal ornithine decarboxylase activity. Transport of dietary lipid into mesenteric lymph was depressed 24 hours after an ischemic insult, yet it returned to the normal level 48 hours after ischemia-reperfusion. The recovery of the lipid transport normally observed at 48 hours after ischemia-reperfusion was attenuated by the H1 antagonist.

CONCLUSIONS

The beneficial effects of histamine on the repair of intestinal mucosa after ischemia-reperfusion results from the engagement and activation of the H1 receptor.